Energy autarky of small scale wastewater treatment plants by enhanced carbon capture and codigestion - A quantitative analysis

Municipal wastewater treatment plants (WWTPs) can achieve energy self-sufficiency (autarky) while complying with increasing discharge standards. We evaluated three energy-positive wastewater treatment scenarios classified as "Basic", "Moderate", and "Advanced" configurations. A quantitative mass and energy balance model was developed to analyze the energy recovery potentials of these configurations. Enhanced COD capture, codigestion with locally available biodegradable wastes, and aeration energy optimization were considered as the main approaches to achieve an energy autarky or energy-positive status. Data from existing operating plants were used to validate the model performance. This paper presents a detailed quantitative analysis of two (basic and moderate) energy-neutral or energy-positive wastewater treatment configurations. In addition, a novel and practically feasible energy-positive wastewater treatment scheme incorporating advanced solids separation is presented with energy analysis and a case study. This model can be useful to quickly assess the energy recovery potential of small scale wastewater treatment systems.